The problem of fouling and marine growth of seismic streamer cables, and the effects on the characteristics of the marine seismic streamer cables, with regard to at least drag, steerability, positioning and reception of seismic signals, is well known to persons skilled in the art of marine seismic information acquisition.
Several devices for cleaning deployed marine seismic streamer cables, operating by travelling along the deployed cable while removing e.g., fouling and marine growth, are known in the art, and properly disclosed, such as for example devices disclosed in U.S. Pat. No. 7,145,833 and U.S. Pat. No. 7,409,919.
The need for controlling the position of a deployed marine seismic streamer cable in several directions, typically to a certain depth, and also to follow a particular path as the streamer cable is being towed behind a vessel, is typically met by attaching to the cable, at intervals, steering devices and other devices for communication and control such as e.g., depth control devices often referred to by the term “bird”. In this disclosure of the present invention, when referring to a “bird”, reference is also made to other devices that typically are attached to the streamer cable, in particular devices that are attached to the streamer cable at locations along the streamer cable that are submerged when the streamer cable is deployed. The typical “bird” is equipped with a wing means and/or body elements, extending also outwards from the streamer cable, to perform the function of e.g., actually move to or hold a corresponding part of the streamer cable in a desired position, is usually removeably attached to the streamer cable. That will allow removal of the “bird” at the time when the streamer cable is recovered from sea and wound up on a drum on the towing vessel, as winding the cable on a drum while still having the “bird” with its sharp edged wing, or rudder, attached to the streamer cable would easily cause serious damage to the relatively fragile streamer cable.
The “bird” typically extends significantly away from the streamer cable, typically a distance that is several multiples of the diameter of the streamer cable itself.
Several arrangements for removably attaching a “bird” to a marine seismic streamer cable are well known in the art, such as e.g., from disclosures provided in patent publication No. U.S. 2003/0226488 and U.S. Pat. No. 6,263,823.
Accordingly, when a cleaning device travelling along the deployed marine seismic streamer cable arrives at a position along the cable where it encounters a “bird” attached to the streamer cable, it also encounters an obstacle for its further travel along the streamer cable. Known solutions to this problem are considered complex and far from optimal, e.g., either because they required additional, risky operative effort at sea by the crew to bring the streamer cable to the surface for temporarily removing the “bird” to let the cleaning device pass the point of attachment of the “bird” to the streamer cable, or for removing the cleaner temporarily and reattaching it to the next section of the streamer cable, or because existing cleaning devices that are adapted to pass by a “bird” while it is attached to the streamer cable, typically due to their complexity are not as reliable as one would like, or for that same reason are expensive to acquire, operate and maintain.
Hence, there is a need for a solution to the problem of making a substantially full-length cleaning a deployed marine seismic streamer cable having a plurality of “birds” attached thereto, that is at least one of more reliable, involves less risk both to the crew, is less costly, or solves other related problems that are well-known to those involved in the use, handling and operation of marine seismic streamer cables for marine seismic information acquisition.